1. Field of the Invention
The present invention relates to a process and apparatus for automatically matching and engaging two substantially cylindrical surfaces. At least one of the cylindrical surfaces is a knurling tool for mechanical emboss engraving, particularly of rolls. The embossed rolls are used for embossing sheet materials and the like. Furthermore the present invention relates also to the mechanical engraved plates obtained with such process and means Chemical corrosion can be used to complete the engraving process.
2. Prior Art
At the present state of the art, processes and means for matching two surfaces to engage each other, particularly for mechanical emboss engraving, are both time consuming and repetitive. Most often these processes and means are manual due to the difficulties encountered in automating them. These processes and means, being difficult to obtain, are provided only on relatively expensive machines operated by highly skilled and specialized operators. The process uses a long machine cycle and requires the operator's constant presence and checking. The engraved products obtained with such process and means are very expensive and have poor precision because of inconsistency of the operator's ability and skill. Operation of the manual machine was limited to regular work time because night shifts or expensive overtime was not desirable. Recourse to overtime work was inevitable when preparation time was so extensive that delivery time was also extended. More than one machine could not be used to make the same piece. The stressful character of performing this work, combined with the responsibility connected therewith was very high because an almost finished roll could be damaged by a small lack of attention, and it was usually not possible to remedy the defect in time. A real and present danger was the need for the operators to put their hands in very risky places.
In particular, an operator has the task to move the active surface of a knurling embossing tool, under pressure to mate with a generally cylindrical passive surface to be mechanically engraved or embossed. Generally the size ratio, between one or more tools and the roll to be engraved is from 2 to 10 with reference to diameter and from 10 to 1000 referring to the whole roll length. Thus, in the course of longitudinal working the roll, the knurling tool must be displaced at least longitudinally, a corresponding number of times. Each time the knurling tool is moved it must be checked against the correct matching reference to suitable markers. However, when the longitudinal repetition pitch of the design exceeds 4-5 cm, a substantially double knurling tool length is needed. When the necessary pressure for an embossing process substantially exceeds the power of the machine, the barrel-like shape of the knurling tool is increased. The same knurling tool is used by fractionally varying the axes of inclination of same knurling tool 4-5 cm each time. For this reason the machine is provided with a third range of freedom, a Z axis, in order that this parameter may be adjusted. If the repetitivity of the design to be embossed has a worm trend, an angular excursion of the knurling tool with respect to the roll to be worked was made manually. The knurling tool was moved along its longitudinal axis. Thus, the operations to be made manually, in each working step, are from a minimum of two to a maximum of four. This requirement was a further obstacle to automation since, each design requires a different working cycle, which must be precisely complied with for a good product.